1. Field of the Invention
The present invention relates to an optical device for strain detection, to a method for the measurement of strain by means of this device, and to their application to scales.
2. Description of Related Art
At the present time, optical devices for strain detection utilizing the deformation of a light guide of the optical fiber type permit the performance of a measurement of the strain applied to a fiber by attenuation of the luminous intensity transmitted on account of the modification of the conditions of propagation of the light in the fiber due to this deformation. Devices of the strain gauge type utilizing the abovementioned property of an optical fiber have been described, in particular, in U.S. Pat. No. 4,163,397 or in European patent application No. 0,082,820. The devices such as those described in the abovementioned documents require the implementation of an additional mechanical structure mounted, for example, at the periphery of the fiber, in order to permit the application of strains and of deformations of a periodic nature over the length of the fiber, the measurement of the total strain applied to the fiber being directly related to the attenuation of the intensity of the light transmitted by the fiber subjected to deformation. Even though this type of device effectively permits a measurement of the load or strain exerted on the fiber, it does not however sanction the simple utilization of a device capable of effecting a weight measurement under the required customary operating conditions of precision, of reliability and of accuracy required for this type of measurement apparatus, or even of a device capable of permitting a two-dimensional reading of the strains or loads exerted on a surface, i.e. a reading of a pressure map.